How do they work in the first place? What are the chemicals? Is it possible to reuse / recycle them?
How does the reaction work? I don’t believe that they give off heat…could you see them via infrared or ultraviolet?
Anyone know the straight dope on these little rave toys?
Daylon
There are three components in a Cyalume type glowstick. In the plastic tube is a solution of bis(phenyl) oxalate ester and a fluorescent dye. Inside the glass capsule is a solution of hydrogen peroxide. When you bend the tube and break the glass capsule, the hydrogen peroxide reacts with the oxalate ester and forms phenol (an alcohol) and carbon dioxide.
This reaction excites the electrons in the fluorescent dye, ‘promoting’ them to higher energy levels. When these ‘excited’ dye molecules return to their ground state (the ‘unexcited’ form), they release a photon equal in energy to the difference in energy between the ground state and the excited state. Since the wavelength and hence the color of light emitted by this reaction depends on the energy difference between the excited state and ground state of the dye, different dyes produce different colors. (The green dye is 9,10-bis(phenylethynyl)anthracene.)
You can see the oxalate/peroxide ester here. A more detailed explanation is here. Note that the second explanation is in response to a question from a middle school student, and is written at at least an upper-year undergraduate level. Also, ‘oxalate’ is misspelled in the first sentence, and, as far as I know, the suggested diketodioxetane intermediate has not yet been confirmed. The paragraph beginning “Tetrakis…” refers to luminol chemoluminesence, which is not applied commercially (but may be familiar to those who watch forensic-investigation TV shows because of its application in detecting bloodstains).
The Cyalume reaction is not reversible. Carbon dioxide is one of the products, and reactions producing CO2 are almost never reversible due to its stability. The fluorescent dye, however, remains intact, so it could be recycled, theoretically, if more oxalate and hydrogen peroxide were added. Another implication of CO2 being a product is that the reaction will progress very quickly if the plastic tube is opened.
The components must be chosen carefully to provide a practical lifetime for the product. Glowsticks can be made much brighter by placing them in a bath of hot water; putting them in a freezer slows the reaction down enough to allow the glowstick to last several weeks or months.
The reaction does not give off heat since it is endothermic, but glowsticks which glow in the infrared do exist and could be seen by a thermal imager. It may be difficult to design a glowstick that glows in the ultraviolet, since molecules tend to break apart rather than fluorescing in the UV.
There are ‘reusable glowsticks’ that run on batteries; some are based on LEDs and are available in various colors, including ultraviolet. Some are based on electroluminescence and are available in Indiglo blue-green only. These are a more environmentally-friendly alternative to disposable chemical glowsticks and are sold for use at clubs and raves. On that note, I should mention that, despite the label, the contents of glowsticks are toxic, and should not be ingested if the integrity of the plastic tube is compromised. =]
Wow.
Now THAT is the explanation I was looking for. Kudos to you, Roches! Allow me to bask in your enlightenment.
Daylon
I am stunned into speechlessness. Great information!
Note to self: Never play trivia or scrabble with Roches.
D.